Switch from PyCrypto HMAC to standard python hmac
Switch from PyCrypto HMAC to standard python hmac

This seems to be a wash performance and functionality wise.  It does however
mean one less segment of code that incurs an external dependency.

Change-Id: I6691d95172d7d83eae4b4ed1265ba398b220f501

benoit-canet/pyghmi,openstack/pyghmi,openstack/pyghmi,stackforge/pyghmi